netdev - Re: [PATCH net-next RFC v1 3/4] devlink: Add hierarchy between traps in device level and port level

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Date:   Sun, 6 Sep 2020 18:58:58 +0300
From:   Ido Schimmel <idosch@...sch.org>
To:     Aya Levin <ayal@...lanox.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jiri Pirko <jiri@...lanox.com>, netdev@...r.kernel.org,
        Moshe Shemesh <moshe@...lanox.com>,
        Eran Ben Elisha <eranbe@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next RFC v1 3/4] devlink: Add hierarchy between traps
 in device level and port level

On Wed, Sep 02, 2020 at 06:32:13PM +0300, Aya Levin wrote:
> Managing large scale port's traps may be complicated. This patch
> introduces a shortcut: when setting a trap on a device and this trap is
> not registered on this device, the action will take place on all related
> ports that did register this trap.

I'm not really a fan of this and I'm not sure there is precedent for
something similar. Also, it's an optimization, so I wouldn't put it as
part of the first submission before you gather some operational
experience with the initial interface.

In addition, I find it very unintuitive for users. When I do 'devlink
trap show' I will not see anything. I will only see the traps when I
issue 'devlink port trap show', yet 'devlink trap set ...' is expected
to work.

Lets assume that this is a valid change, it would be better implemented
with my suggestion from the previous patch: When devlink sees that a
trap is registered on all the ports it can auto-register a new
per-device trap and user space gets the appropriate notification.

> 
> Signed-off-by: Aya Levin <ayal@...lanox.com>
> ---
>  net/core/devlink.c | 43 +++++++++++++++++++++++++++++++++----------
>  1 file changed, 33 insertions(+), 10 deletions(-)
> 
> diff --git a/net/core/devlink.c b/net/core/devlink.c
> index b13e1b40bf1c..dea5482b2517 100644
> --- a/net/core/devlink.c
> +++ b/net/core/devlink.c
> @@ -6501,23 +6501,46 @@ static int devlink_nl_cmd_trap_set_doit(struct sk_buff *skb,
>  	struct devlink *devlink = info->user_ptr[0];
>  	struct devlink_trap_mngr *trap_mngr;
>  	struct devlink_trap_item *trap_item;
> +	struct devlink_port *devlink_port;
>  	int err;
>  
> -	trap_mngr = devlink_trap_get_trap_mngr_from_info(devlink, info);
> -	if (list_empty(&trap_mngr->trap_list))
> -		return -EOPNOTSUPP;
> +	devlink_port = devlink_port_get_from_attrs(devlink, info->attrs);
> +	if (IS_ERR(devlink_port)) {
> +		trap_mngr =  &devlink->trap_mngr;
> +		if (list_empty(&trap_mngr->trap_list))
> +			goto loop_over_ports;
>  
> -	trap_item = devlink_trap_item_get_from_info(trap_mngr, info);
> -	if (!trap_item) {
> -		NL_SET_ERR_MSG_MOD(extack, "Device did not register this trap");
> -		return -ENOENT;
> +		trap_item = devlink_trap_item_get_from_info(trap_mngr, info);
> +		if (!trap_item)
> +			goto loop_over_ports;
> +	} else {
> +		trap_mngr = &devlink_port->trap_mngr;
> +		if (list_empty(&trap_mngr->trap_list))
> +			return -EOPNOTSUPP;
> +
> +		trap_item = devlink_trap_item_get_from_info(trap_mngr, info);
> +		if (!trap_item) {
> +			NL_SET_ERR_MSG_MOD(extack, "Port did not register this trap");
> +			return -ENOENT;
> +		}
>  	}
>  	return devlink_trap_action_set(devlink, trap_mngr, trap_item, info);
>  
> -	err = devlink_trap_action_set(devlink, trap_mngr, trap_item, info);
> -	if (err)
> -		return err;
> +loop_over_ports:
> +	if (list_empty(&devlink->port_list))
> +		return -EOPNOTSUPP;
> +	list_for_each_entry(devlink_port, &devlink->port_list, list) {
> +		trap_mngr = &devlink_port->trap_mngr;
> +		if (list_empty(&trap_mngr->trap_list))
> +			continue;
>  
> +		trap_item = devlink_trap_item_get_from_info(trap_mngr, info);
> +		if (!trap_item)
> +			continue;
> +		err = devlink_trap_action_set(devlink, trap_mngr, trap_item, info);
> +		if (err)
> +			return err;
> +	}
>  	return 0;
>  }
>  
> -- 
> 2.14.1
>